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- Faser-Bragg Gitter (1)
- Fiber Bragg grating (1)
- Fiber Bragg gratings (1)
- Fiber bragg grating (1)
- Fibre optical sensing (1)
- Field conditions (1)
- Finite element methods (1)
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- Hochdynamische Untersuchungen (1)
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- Impact (1)
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- Instrumentierte Eindringprüfung (1)
- Intumescence (1)
- Klebstoffe (1)
- Kraftabhängige Funktion (1)
- Lamb wave (1)
- Large scale soil test field (1)
- Laser-based displacement measuring system (1)
- Leak detection (1)
- Legged robots (1)
- Linear sensor (1)
- Localization of gas sources (1)
- Magneto-optischer Sensor (1)
- Magnetostriction (1)
- Magnetostrictive metal coating (1)
- Magnetostriktive Beschichtung (1)
- Maschinennachgiebigkeit (1)
- Measurement (1)
- Measurement uncertainty (1)
- Membrane-based linear gas sensor (1)
- Metal oxide semiconductor (1)
- Methane measuring (1)
- Micro UAV (1)
- Miniaturized sensor device (1)
- Mobile Robot (1)
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- Moisture measurements (1)
- Monitoring of CO2 (1)
- Multi sensor device (1)
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- NDT Inspection (1)
- Nano UAV Swarm (1)
- Nanocomposites (1)
- New sensor principles (1)
- Nitroaromaten (1)
- Odor localization (1)
- Oil (1)
- Olfaction (1)
- Particle filter (1)
- Passive sensor interface (1)
- Passive sensors (1)
- Pattern recognition methods (1)
- Piezoresistive accelerometer (1)
- Plume tracking (1)
- Prototyp (1)
- Pump control (1)
- Quadrokopter (1)
- Quadruped robots (1)
- Quality Infrastructure (1)
- Quantification of gas concentrations (1)
- RAM packages (1)
- RFID Sensor systems (1)
- RFID based sensors (1)
- Radioactive (1)
- Red Phosphorus (1)
- Remote gas sensor model (1)
- Robotik (1)
- Schadensfrüherkennung (1)
- Selbstkalibrierung (1)
- Selective permeability (1)
- Self-diagnostic fiber optical sensor (1)
- Sensor (1)
- Sensor planning (1)
- Setup and Validation (1)
- Single cable system (1)
- Soil test field (1)
- Spatially distributed monitoring (1)
- Sphärische Indenter (1)
- Standard gas generator (1)
- Strain (1)
- Strain measurements (1)
- Structural Health Monitoring (1)
- Structure health monitoring (1)
- Suche und Lokalisierung von gasförmigen Gefahrstoffquellen (1)
- System adhesive/ strain gauge (1)
- TDLAS (1)
- Temperaturabhängige Prüfung (1)
- Temperature and Frequency Compensation (1)
- Temperature behavior (1)
- Temperature calibration (1)
- Temperature characteristics (1)
- Temperature dependent and high dynamic load tests (1)
- Temperaturkompensation (1)
- Test (1)
- Tomographic reconstruction of gas plumes (1)
- Tunable Diode Laser Absorption Spectroscopy (TDLAS); UAV-REGAS (1)
- UHF antenna (1)
- Urban air monitoring (1)
- Vereinfachtes Verfahren (1)
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- agricultural economy (1)
- embedded sensor (1)
- environment (1)
- fluorescence (1)
- gas analysis (1)
- poultry odorous air monitoring (1)
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Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (28)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (28)
- 1 Analytische Chemie; Referenzmaterialien (4)
- 1.9 Chemische und optische Sensorik (4)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (4)
- 3 Gefahrgutumschließungen; Energiespeicher (1)
- 3.3 Sicherheit von Transportbehältern (1)
- 6 Materialchemie (1)
- 6.7 Materialsynthese und Design (1)
- 8.3 Thermografische Verfahren (1)
The exploration of condensed phase mechanisms such as charring and intumescence has been pushed forward in the last decades, since it is believed that focusing on these concepts will bring materials closer to an efficient and ecologically friendly fire retardancy. They promise to concentrate efficient fire retardancy at the key position between pyrolysis zone and gas phase. Examples of residue/char forming and intumescent materials are used to illustrate the influence of mass and heat barrier effects on the fire behavior of materials and general results are presented. A comprehensive understanding of the mechanisms and structure-property relationships in fire retardancy is presented.
Wireless sensor network for long-term structural health monitoring of buildings and infrastructures
(2009)
Damage commonly occurs in buildings when a component fails suddenly with a
partial or total collapse as a consequence. This type of event leads to serious damage to property
and if it is a bridge or a large hall, then people in particular are at risk. The often great age of
bridges and the increasing volume of traffic (particularly heavy traffic) which they are expected
to carry are in clear contradiction to each other. Thus the probability increases that the loadbearing
capacity of a bridge decreases rapidly and often unnoticed with sometimes dire
consequences.
In order to prevent such accidents, the Federal Institute for Materials Research and Testing is
currently developing a special radio-based, self-configuring measuring system in cooperation
with the Berlin-based ScatterWeb Company. This measuring system consists of a number of
identically designed sensor nodes which are self-sustaining, need no wiring, can act as both
transmitters and receivers and are equipped with a special sensor technology making long-term
monitoring of buildings or engineering facilities possible. The sensor unit uses strain gauges for
stress analysis and contains interfaces for additional sensors. The system in particular applies to
buildings and structures for transport and traffic and large-scale industrial facilities, where a
subsequent wiring installation is difficult or impossible.
The project SIGRID investigates and assesses possibilities to enhance the safety and security of
dangerous goods transports through the use of the latest RFID-technology. This technology can be used to
greatly enhance the transparency of the supply chain and aid logistics companies in complying with regulations.
In the context of SIGRID, customized RFID-Sensor-Tags have been developed that monitor dangerous
goods during transport and help to prevent hazards by allowing timely countermeasures. In the case of a dangerous
goods accident, the available information about the type, amount and condition of the dangerous goods
can be used to accurately inform the relief forces. Unavailable or inaccurate information represents a significant
problem for the relief forces. This often leads to a delay in the rescue operation, because relief forces
must be aware of the substances involved to protect themselves effectively against them. SIGRID aims to
close this information gap. To verify the practicability of the underlying concepts, a demonstrator will be
build and tests of realistic scenarios will be conducted.
In preliminary work, gas sensors in linear form based on the measuring principle of gas selective permeability through a membrane were developed and introduced for the detection and quantification of gas concentrations. In this study, first experimental results are presented for adapting the technology for measuring methane (CH4). A material with suitable selective permeability was identified and utilized in a sensor setup containing the gas selective membrane and a reference membrane, both integrated in a measuring cell, to which a gas stream with defined CH4 concentrations was applied. The results prove the sensor's capability for measuring methane and indicate further application potential of the method, e.g., as a robust field monitoring technology, since CH4 is the major component of natural gas, town gas, and fracking gas.
Insect behavior is a common source of inspiration for roboticists and computer scientists when designing gas-sensitive mobile robots. More specifically, tracking airborne odor plumes, and localization of distant gas sources are abilities that suit practical applications such as leak localization and emission monitoring. Gas sensing with mobile robots has been mostly addressed with ground-based platforms and under simplified conditions and thus, there exist a significant gap between the outstanding insect abilities and state-of-the-art robotics systems. As a step toward practical applications, we evaluated the performance of three biologically inspired plume tracking algorithms. The evaluation is carried out not only with computer simulations, but also with real-world experiments in which, a quadrocopter-based micro Unmanned Aerial Vehicle autonomously follows a methane trail toward the emitting source. Compared to ground robots, micro UAVs bring several advantages such as their superior steering capabilities and fewer mobility restrictions in complex terrains. The experimental evaluation shows that, under certain environmental conditions, insect like behavior in gas-sensitive UAVs is feasible in real-world environments.
One of the main unsolved issues of under-ground storages for, e.g., CO2, H2, and natural gas is the comprehensive surveillance of these areas with reasonable effort and costs. Conventional sensors (e.g., soil air probes or borehole probes), however, can only be used for punctual or locally limited measurements; further their application can cause structural influences (invasive application).
In this paper, we describe in detail the setup of a CO2 injection soil test field. This test field will be used to enhance and validate an innovative ap-proach for distributed subsurface monitoring of gas storage areas. To the author’s knowledge, this is the first time that, for this purpose, a test field is built in an application relevant scale.
A high-performance fiber Bragg grating-based (FBG) sensor device has been developed for the detection of small magnetic fields. Based on a smart multilayer jacket around the fibre over the physical length of the FBG, magnetic fields generated by rotating machine parts, power generators or power cable can be easily detected, analysed and evaluated. Consequently, this innovative, on-line and non-contact inspection method results in an increase in quality and reliability of high-performing machine parts, devices and cables. The basic physical principle is based on a magnetostrictive multilayer system that strains the high-resolution FBG element in presence of magnetic fields. Subsequently, a fixed relationship between induced magnetic field and wavelength change of the FBG element describes the characteristic sensitivity curve. Intensive tests regarding characterisation of this magnetic field FBG sensor have been carried out and its performance has been evaluated.
One of the more difficult tasks for structural health monitoring is the continuous evaluation of the stability and load capacity of the building materials. This knowledge can be won, e.g., by taking material samples at the examining place with the drawback of partly destroying the structure. To avoid this, modern sensor and communication technologies offer promising methods for non-destructive testing. To address the tasks for monitoring of concrete structures, in the presented study, different sensors were combined with RFID transponders and embedded in concrete components.
A new concept for the self-diagnosis of embedded fiber Bragg grating (FBG) strain sensors was developed, simulated and experimentally tested. This concept is based on a magnetostrictive metallic layer directly coated on the fibre cladding over the grating segment of the FBG sensor, so that an on-demand external magnetic field in a millitesla scale can produce a controllable artificial strain as an indication signal for the remote optical interrogator. The relationship between the pre-defined magnetic field and its induced Bragg wavelength shift characterizes this validation concept. Any deviation of the local bonding state of the interfaces from the initial or/and any change of shear strain transferring mechanism from composite matrix to the optical fibre core will result in alterations in this sensitive relationship, and thus triggers an immediate alert for a further inspection. The finite element method is used to simulate the strain of this configuration as result of different values of the magnetic field in order to optimize the geometrical sensor parameters. The simulations are verified by experiments results. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sensors integrated into devices and structures provide essential data to control, optimize or manage machines and structural components. In the last years, processes, applications and machine parts became more and more intelligent. Consequently, the need for sensor validation increased significantly in order to rely on sensor data and measurement results.
Structure-integrated fibre optic strain sensors, such as fiber Bragg gratings (FBG), are of special interest in the composite manufacturing industry. This type of sensor makes it possible to gain information and to collect measurement data about entire production processes and whole life-time cycles of composite-made machine parts and structures. However, validation concepts and approaches for this type of sensors are barely reported in literature. Furthermore, all the reported activities have the drawback that the sensor diagnosis strategy is implemented as limited mathematical models and/or complex time-consuming spectral analysis tools which are applied in data post-processing loops. However, to automate sensor validation and to apply real-time and in-field sensor fault detection, it is necessary to acquire measurement data and information about the measurement reliability at the same time.
Berlin Main Station is the largest multi-level station in Europe. Its daily passenger number amounts to over 300.000. Structures built for such a large number of people require a high-level safety standard. The station was built on the inner city site of the historic Lehrter Bahnhof. The conditions for building and start of operation were challenging by several reasons. The typical sandy ground with a high level of groundwater makes the permanent static stability of such a complex structure difficult. Several completed, ongoing, and planned construction activities in the immediate vicinity of the station influence the ground settlement of the whole area. On basis of the structural design an impact prediction was calculated, which expected certain vertical displacements particularly between the single columns of the outer concrete bridges of the building. These columns support the glass roof construction, which only allows a defined limit of displacement. In order to avoid damage, a concept for monitoring and adjusting potentially occurring displacements was developed for installation at the outer bridges of the station.
BAM is the German Federal Institute for Materials Research and Testing and the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste. In context with safety assessment of RAM packages BAM performed numerous drop tests in the last decades. The tests were mostly accompanied by extensive and various measurement techniques especially by instrumented measurements with strain gages and accelerometers. The procedure of drop testing and the resulting measurement analysis are the main methods to evaluate the safety against mechanical test conditions. Measurement techniques are dedicated to answer questions in regard to the structural integrity of a RAM package, the mechanical behavior of the prototype as well as of its content under impact conditions.
Test results like deceleration-time functions constitute a main basis for the validation of assumptions in the safety analysis and for the evaluation of numerical calculations. In this context the adequate selection of accelerometers and measurement systems for the performance of drop tests is important. Therefore it is not only necessary to find suitable positions for the accelerometers at the test specimens, but also to consider technical boundary conditions as e.g. temperature.
Nitroaromaten und insbesondere Trinitrotoluol (TNT) sind weit verbreitete Spreng- und Umweltschadstoffe. Die größte Herausforderung bei der Detektion von TNT in der Gasphase ist der geringe Dampfdruck. Derzeit werden vielerorts günstige, schnelle, handliche und einfach zu bedienende Alternativen zur klassischen TNT-Analytik entwickelt. Aktuell existieren keine einheitlichen Richtlinien für Sprengstoffsensoren. Hier wird die Entwicklung eines Messplatzes zur Validierung von Sprengstoffsensoren sowie die Erprobung eines kompakten Mustersensors vorgestellt.
Completely embedded sensor systems for long-term
operation offer innovative possibilities for structural health
monitoring of concrete structures. Measuring of relevant
parameters, e.g., temperature, humidity, or indication of
corrosion can be performed with low energy sensors. This allows
to implement passive RFID sensor systems without cable
connection and battery, which are power supplied exclusively by
the electromagnetic field from the external reader device. To
evaluate characteristics and conditions of this concept, a
systematical investigation of the transmission characteristics with
variation of relevant parameters, as communication frequency,
installation depth, type of concrete, moisture content, etc. is
currently carried out in an interdisciplinary research project at
BAM. First results are presented in this paper.
Embedded wireless sensor systems for long-term SHM and corrosion detection in concrete components
(2017)
State-of-the-art communication standards like RFID and Bluetooth Low Energy enable the development of sensor systems which can be completely embedded into concrete components for long-term SHM and early damage detection. Objective of the project KonSens which is carried out at BAM is the development, implementation, and validation of sensors for measuring of Parameters relevant for corrosion, like moisture, pH value, and electrical conductivity, inside steel reinforced concrete components. The primarily addressed application is detection and evaluation of corrosion processes in concrete bridges.
In contrast to cable connected sensors, embedded wireless sensors avoid any pathways for intrusion of moisture and chemicals, e.g., chlorides which could trigger corrosion activity. To allow for long-term, ideally life-time operation, the once embedded sensor systems must work highly energy efficient. One option are passive RFID sensor systems, which work without battery. The energy is transmitted to the system through the electromagnetic field, even to operate sensors. A crucial parameter is the transmission depth in concrete. First experiments with RFID sensors working at frequencies of 13.56 MHz (HF) and 868 MHz (UHF) embedded in concrete specimen resulted positive for transmission depths of up to 13 cm, which is quite promising, considering that corrosion would appear first at the top level of rebars.
A second generation of passive RFID sensor systems has been implemented with improved antenna design. Current experiments using these systems focus on the Transmission characteristics in terms of transmission depths and the impact of concrete moisture. Low-energy humidity sensors are used and analysed regarding their capability for measuring the material moisture. Additionally, a relation between transmitted power to the embedded sensor and the moisture content of the concrete specimen caused by energy absorption can be presumed and is under systematic investigation.
Damages in infrastructure due to moisture amount to billions of Euros every year. For a more predictive structural health monitoring in civil engineering, the detection and monitoring of hazardous moisture in steel reinforced concrete constructions is of high interest. The sensors have to be wireless, elsewise they weaken the concrete cover of the rebars. The lifetime of such constructions is normally decades, thus the sensors have to be battery-free and fully passive. Considering these requirements, passive RFID-based sensors are developed. Communication and energy supply are realized wireless via the electromagnetic field of a RFID transmitter. The passive RFIDbased sensors are embedded into the concrete to enable the monitoring of moisture transport in porous materials. Results of the hydration process are shown.
Because ammonia and its reaction products can cause considerable damage to human health and ecosystems, there is a need for reliably operating and reversibly interacting sensor materials to monitor traces of gaseous ammonia in ambient air, which at best can be used on-site for in-the-field measurements. Herein, the development of a sensor material for gaseous ammonia in the lower ppm to ppb range using optical fluorescence as transduction mechanism is presented. A fluorescent dye, which shows reversible fluorescence enhancement in the presence of ammonia is incorporated into a polymer matrix, the latter to ensure the accumulation of ammonia. The sensor material is integrated into a prototype of a miniaturized sensor device, facilitating long-term operation. To calibrate the optical sensor system a gas standard generator, producing standard gas mixtures, is used, leading to a sensitivity down to lower ppm concentrations of ammonia.
This paper is a further research on the topic of the complete embedding of radio frequency identification (RFID) sensors in concrete. The focus is on the antenna of the transponder. Earlier investigations of different RFID technologies, embedded in concrete, showed a difference in energy transmission. The transmission through concrete at ultra high frequency (UHF), in spite of the large signal range, does not match the targeted application specific task. Therefore, the antenna characteristics have been examined more closely. The antenna is an important component for the application of RFID. Through the antenna, energy and data transfer takes place, so it is important to design an optimal antenna to accomplish a maximum embedding depths in concrete. To identify the optimal antenna geometry, different UHF antenna types were selected and investigated. An experimental comparison was performed to gain more information about the damping behavior and antenna characteristics in concrete.
This paper deals with the development and investi-gation of a volatile organic compound (VOC) system for differ-ent scenarios. The integrated multi-sensor unit can detect dif-ferent gases through the integrated 3-fold VOC sensor, where-by a continuous measurement takes place. The system-integrated flow control, with pump and flow sensor, allows the gas molecules to be transported directly to the VOC sensor. The entire measurement is permanently stored on an integrat-ed Secure Digital (SD) card. If the previously determined limit range is exceeded, an alarm is generated. Due to the combina-tion of different components, numerous applications are possi-ble. The system is the first step or a tool towards further devel-opments in the field of gas sensors and is primarily used for the validation of chemically based gas sensors, and it is still largely extended by application-specific influences.
Piezoresistive accelerometers use a strain-sensing element, generally made of semiconductor material, e.g., silicon to convert the mechanical motion into an electrical signal. This element is usually designed in form of a cantilever beam loaded with a mass. Acceleration causes bending of the beam, which produces a change of electrical resistance proportional to the applied acceleration.
Main advantages of piezoresistive accelerometers in comparison to other types, e.g., piezoelectric and capacitive, is their robust and highly dynamic behavior, which qualifies them for application in high impact shock applications. Mechanical damping is typically implemented with silicon oil in a way that the output signal is undistorted over a wide frequency range. These characteristics principally qualify them for the application in drop tests carried out at BAM, for which they are calibrated over the frequency range from 1 to 4 kHz. However, using silicon oil for damping, has the drawback of temperature dependent change of its viscosity, leading to temperature dependent deviation of the accelerometer’s sensitivity.
This study presents experimental results of the temperature behavior of a piezoresistive accelerometer with a dynamic range up to ±5000 g.
This type of accelerometer is applied for drop tests which are partially performed at temperatures of -40 or +100 °C.
In Glasfasern eingeschriebene Bragg-Gitter (FBG: fibre-based Bragg gratings) sind über die Verschiebung der Bragg-Wellenlänge in der Lage, Stauchungen und Dehnungen von Glasfasern hochgenau zu erfassen. In Kompositwerkstoffe eingebettete faseroptische Sensoren können Bauteile bezüglich ihrer mechanischen Integrität überwachen und früh-zeitig Informationen über Materialveränderungen gewinnen.
Um die Zuverlässigkeit eines solchen Sensors zu gewährleisten, ist es wichtig, die korrekte Funktion des Sensors im Verbund mit der Werkstoff-Matrix on-line und in-situ sicherzu-stellen. Im Rahmen des DFG-Projekts FAMOS² (FAser-basierter Magneto-Optischer SchichtSensor) wurde ein selbstdiagnosefähiger Schichtsensor entwickelt, der mit Hilfe von magnetostriktiven Aktorschichten aus Nickel bzw. Eisen-Nickel validiert werden kann.
Der FAMOS²-Schichtsensor wird durch ein PVD (physical vapour deposition)/ECD (electro-chemical deposition) Hybridschichtsystem realisiert, das auf dem Fasermantel im Bereich des FBG haftfest, homogen und langzeitfunktional abzuscheiden ist. Dabei wird in einem ersten Schritt ein etwa 100 Nanometer dünnes PVD-Schichtsystem aus Chrom und Kupfer als Haftvermittler auf der Glasfaser bzw. als leitfähige Startschicht für den nachfolgenden ECD-Prozess abgeschieden. Um eine rotationssymmetrische Schich-tabscheidung zu gewährleisten, erfolgt während der PVD-Beschichtung eine Rotation der Glasfasern. In einem zweiten Schritt wird dann unter Verwendung eines klassischen Watts-Elektrolyten in einer speziell entwickelten ebenfalls rotationssymmetrisch aufgebau-ten ECD-Durchströmungszelle dann die etwa 30 Mikrometer dicke, magnetostriktive Ak-torschicht auf dem PVD-Schichtsystem abgeschieden, im Vergleich sowohl reine Nickel-Schichten als auch Nickel-Eisen-Schichten.
Ein äußeres Magnetfeld dehnt die magnetostriktive Aktorschicht und damit auch die Faser reversibel. Diese Dehnung führt zu einer Verschiebung der Bragg-Wellenlänge, welche direkt mit der Stärke eines zu messenden oder zu Validierungszwecken vorgegebenen Magnetfeldes korreliert. Die Anpassung der Beschichtungsverfahren an die Fasergeome-trie und die mechanischen Eigenschaften der Hybridschichten werden hinsichtlich der me-chanischen Integrität des faseroptischen Sensors diskutiert und der Nachweis der Selbst-diagnosefähigkeit erbracht.
BAM is the German Federal Institute for Materials Research and Testing and the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste. In context with safety assessment of RAM packages BAM performed numerous drop tests in the last decades. The tests were mostly accompanied by extensive and various measurement techniques especially by instrumented measurements with strain gages and accelerometers.
The procedure of drop testing and the resulting measurement analysis are the main methods to evaluate the safety against mechanical test conditions. Measurement techniques are dedicated to answer questions in regard to the structural integrity of a RAM package, the mechanical behavior of the prototype as well as of its content under impact conditions.
Test results like deceleration-time functions constitute a main basis for the validation of assumptions in the safety analysis and for the evaluation of numerical calculations. In this context the adequate selection of accelerometers and measurement systems for the performance of drop tests is important. Therefore it is not only necessary to find suitable positions for the accelerometers at the test specimens, but also to consider technical boundary conditions as e.g. temperature.
Insect behavior is a common source of inspiration for roboticists and computer scientists when designing gas-sensitive mobile robots. More specifically, tracking airborne odor plumes and localization of distant gas sources are abilities that suit practical applications such as leak localization and emission monitoring. Gas sensing with mobile robots has been mostly addressed with ground-based platforms and under simplified conditions and thus, there exist a significant gap between the outstanding insect abilities and state of the art robotics systems. As a step towards practical applications, we evaluated the performance of three biologically inspired plume tracking algorithms. The evaluation is carried out not only with computer simulations, but also with real-world experiments in which, a quadrocopter-based micro Unmanned Aerial Vehicle autonomously follows a methane trail towards the emitting source. Compared to ground robots, micro UAVs bring several advantages such as their superior steering capabilities and fewer mobility restrictions in complex terrains. The experimental evaluation shows that, under certain environmental conditions, insect like behavior in gas-sensitive UAVs is feasible in real world environments.
Limited access to the object of relevance is often an essential problem in testing routines, e.g. for non-destructive testing of industry facilities or components of means of transportation. The presented project is about the development of a non-destructive testing method for application over great distances (up to 100 m). The method is based on directed excitation and measuring of Lamb waves (guided waves). It enables an effective differentiation of structural and defective indications as well as a classification of different defect types.
The advantage of guided waves is the ability of propagation over great distances. This offers innovative possibilities for the investigation of large or difficult to access constructions. The testing method can be helpful in a broad variety of applications. It is useable for the characterization of plane or cylindrical, thin-walled surfaces of metal or fiber laminated materials. Particularly the investigation of aircraft wings and other aerospace components as well as the investigation of pipelines are addressed fields of application.
In this paper, we show that a micro unmanned aerial vehicle (UAV) equipped with commercially available gas sensors can address environmental monitoring and gas source localization (GSL) tasks. To account for the challenges of gas sensing under real-world conditions, we present a probabilistic approach for GSL that is based on a particle filter (PF). Simulation and real-world experiments demonstrate the suitability of this algorithm for micro UAV platforms.
In industrial environments, airborne by-products such as dust and (toxic) gases, constitute a major risk for the worker’s health. Major changes in automated processes in the industry lead to an increasing demand for solutions in air quality management. Thus, occupational health experts are highly interested in precise dust and gas distribution models for working environments. For practical and economic reasons, high-quality, costly measurements are often available for short time-intervals only. Therefore, current monitoring procedures are carried out sparsely, both in time and space, i.e., measurement data are collected in single day campaigns at selected locations only. Real-time knowledge of contaminant distributions inside the working environment would also provide means for better and more economic control of air impurities. For example, the possibility to regulate the workspace’s ventilation exhaust locations can reduce the concentration of airborne contaminants by 50%.
To improve the occupational health and safety of (industrial) workplaces, this work aims for developing a swarm of gas-sensitive aerial nano robots for monitoring indoor air quality and for localizing potential emission sources.
Es wird ein vereinfachtes Verfahren für die Bestimmung und Implementierung der Maschinennachgiebigkeit bei der Verwendung eines sphärischen Indenters dargestellt. Die Maschinennachgiebigkeit wird bei deutlicher Kraftabhängigkeit als Funktion der Kraft in die Auswertung implementiert. Als sensitiver Kennwert dient der aus der instrumentierten Eindringprüfung an Härtevergleichsplatten ermittelte Eindringmodul.
Structural Health Monitoring (SHM) has become very important in today's rapidly developing time. High buildings, large bridges and complex technical structures need to be monitored continuously and this over long periods.
Visual monitoring cannot evaluate the internal condition of building structures. Thus, material embedded sensors are needed. Cable connection of these sensors pose the disadvantage of weak spots and water intrusion. For concrete embedded sensors the use of batteries is not convenient, because of limited lifetime, difficult charging, and generation of electrical waste.. Hence, monitoring should be implemented preferentially with firmly embedded passive RFID sensor modules. However, since the concrete structure forms an electromagnetically reflective and absorbing barrier, only limited energy can be transmitted to the module. This project requires a highly energy-saving system, which can record different sensor parameters at critical points.
This paper describes a wireless mobile prototype able to perform optical measurements by means of a miniatur-ized spectrometer for low light analysis, e.g. fluorescent sensors. Evaluations, calculations, calibration management and result display are performed by a computer or a standard tablet. The device was designed primarily to detect traces of oil in drinking or ground water and for the analyses of crude oils. However, it can also address a wide range of fluorescent sensors. The fast and user-friendly inspection of water quality or oil properties, as well as the adaptability and mobility, make the device attractive for a variety of users. Further application areas could be easily imple-mented by adapting the optics and the software (database, data processing and calibration plots, etc.)
In this paper, we introduce a nano aerial robot swarm for Indoor Air Quality (IAQ) monitoring applications such as occupational health and safety of (industrial) workplaces. The robotic swarm is composed of nano Unmanned Aerial Vehicles (UAVs), based on the Crazyflie 2.0 quadrocopter, and small lightweight Metal Oxide (MOX) gas sensors for measuring the Total Volatile Organic Compound (TVOC), which is a measure for IAQ. An indoor localization and positioning system is used to estimate the absolute 3D position of the swarm similar to GPS. A test scenario was built up to validate and optimize the swarm for the intended applications. Besides calibration of the IAQ sensors, we performed experiments to investigate the influence of the rotor downwash on the gas measurements at different altitudes and compared them with stationary measurements. Moreover, we did a first evaluation of the gas distribution mapping performance. Based on this novel IAQ monitoring concept, new algorithms in the field of Mobile Robot Olfaction (MRO) are planned to be developed exploiting the abilities of an aerial robotic swarm.
Linear sensor for areal subsurface gas monitoring - calibration routine and validation experiments
(2014)
Membrane based linear gas sensors and fiber optical sensors feature similar geometries and complement each other in quantities to be measured. To the author's best knowledge, it is the first time that these sensors are combined to a multifunctional sensor for distributed measuring of gas concentrations, temperature, and strain. Objective is a comprehensive monitoring of underground gas storage areas. In the presented project a 400 m² test site and a corresponding laboratory system were just built up to characterize, validate, and optimize the combined sensor. Application of the sensor lines in a grid structure should enable spatial resolution of the measurement data and early detection of relevant events, as gas leakage, temperature change, or mechanical impact. A Calibration routine was developed which can be applied subsequent to underground installation. First measurement results indicate the potential of the method, with regard to highly topical energy transport and storage issues.
Multichannel measuring systems are used to measure strains and accelerations during drop tests of containments for dangerous goods. Conventional systems require cabling of each sensor and co-falling of the cable harness, causing problems in the test preparation and execution. Promising results of a single cable measuring system, consisting of measuring modules with data bus connection and local data acquisition were obtained in laboratory investigations and full-scale drop tests.
Comprehensive monitoring of pipelines over their full length is technically difficult and expensive. Considering a cost-benefit ratio it is reasonable to implement monitoring solutions in pipeline segments, which bear a high risk potential, like residential areas, construction sites, slopes, street or river crossings. Still such segments can measure up to several hundred meters in length, demanding for monitoring solutions that extend along such distances and enable fast response. Point wise sensing and periodical surveillance have clear drawbacks, particularly regarding early damage detection. Fibre optic sensors enable distributed sensing of temperature and strain, but they offer very limited possibilities for measuring gas concentrations. Linear membrane-based gas sensors enable the monitoring of gas concentrations alongside a pipeline. Such line-sensors are implemented in form of flexible tubes and can be arranged inside or outside the pipeline (also underwater or within the subsurface), corresponding to the technical requirements. The measuring method combines the gas specific diffusion rates through a membrane with Dalton’s law of partial pressures and enables the calculation of gas concentrations or the detection of a change of the gas composition. The objective is to detect gas leakages fast and with high reliability. Furthermore, the calibrated system enables to estimate the spatial extent of a leakage. So far the gas concentration measurement is tested for oxygen, carbon dioxide, methane; further gases should follow, e.g. hydrogen, carbon monoxide or mixtures like natural gas. The paper introduces in the different operating modes of line-sensors. A near real-time approach will be demonstrated to quantify the impact of a gas leak on the near environment. This approach is based on a critical length describing the expansion of the leaking gas.
The combination of radio-frequency identification (RFID) tags with different types of sensors offers excellent potential for applications with regard to identification, diagnosis, and monitoring. This should be demonstrated by means of two examples of actual developments carried out by the Federal Institute for Materials Research and Testing (BAM). The Identification and diagnosis of concrete components is a major task in the maintenance of critical infrastructure, for instance concrete bridges with heavy traffic volume. A feasibility study investigates the application of RFID sensor systems for this task. The second example reviews the transportation of dangerous goods. Using modern technologies enables promising possibilities to reduce accidents and to avoid non-conformity with transportation regulations. Project results demonstrate an innovative technical solution for monitoring of dangerous goods transports with RFID sensor systems.
The measurement characteristics of every conventional accelerometer are temperature dependent - often to an extent which is highly relevant for the addressed application. For instance, at BAM Container drop tests are performed to investigate and evaluate the structural integrity of Containers for transport and storage of dangerous goods. Often, the test program includes drop tests at specific temperatures, also as part of approval procedures. The applied sensors are exposed to these test conditions and get influenced by them. Acceleration sensors show a considerable temperature influence on their fünction and characteristics. Particularly the damping mechanism of the seismic mass is a critical part. In regard to such applications, capable equipment and methods are required to consider and investigate this aspect in an adequate way. A fortiori as Manufacturer’s infonnation often is deficient. This study presents the setup and results of a method for testing and calibration of acceleration sensors under high dynamic irnpact. It combines a Hopkinson Bar with a temperature chamber.
In the near future, it will be important to adopt innovative approaches and technologies in order to further guarantee the reliability and availability of the highway network. New tools are therefore needed in order 'to obtain in-depth information about the condition of bridges and its development early enough before significant, precarious damage cases occur. In 2011, the research program "Intelligente Brücken (Smart Bridges)" was launched by the BASt together with the BMVI to evolve systems for information and holistic evaluation for bridge structures as a supplement to the current inspection-based maintenance management. Several projects dealt with the topic in the last few years and provided guidelines and a solid basis to move towards a first implementation considering the input of all research projects carried out so far.
Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT. In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined.
A monitoring method is introduced that creates, in near real-time, two-dimensional (2D) maps of the soil gas distribution. The method combines linear gas sensing technology for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct spatial and temporal resolved gas distribution maps. A weighted iterative algebraic reconstruction method based on Maximum Likelihood with Expectation Maximization (MLEM) in combination with a source-by-source reconstruction approach is introduced that works with a sparse setup of orthogonally-aligned linear gas sensors. The reconstruction method successfully reduces artifact production, especially when multiple gas sources are present, allowing the discrimination between true and non-existing so-called ghost source locations. A first experimental test indicates the high potential of the proposed method for, e.g., rapid gas leak localization.
Damage to buildings occurs if a construction component fails. The result is a partial or total collapse which can be dangerous for people for example if it's a bridge or a large hall. The collapse of the terminal building at the Airport Charles de Gaulle in Paris and the damage at the historic City Archives of Cologne are typical examples of such accidents. Another problem is the contradiction of the increasing volume of traffic (particularly heavy traffic) and the great age of bridges. The probability increases that the load-bearing capacity of a bridge decreases. For example the collapses of the Mississippi Bridge and of the Inntal Motorway Bridge can be seen as results. Therefore it is necessary to control endangered structures during their life span.
In order to prevent these kinds of accidents, the Federal Institute for Materials Research and Testing developed a radio-based, self-configuring measuring system in cooperation with the ScatterWeb Company, Berlin (Germany). This measuring system consists of identically designed sensor modules which are self-sustaining, wireless, act as transmitters and receivers and are equipped with a special sensor technology for long-term monitoring of buildings or engineering facilities. The sensor unit uses strain gauges for stress analysis and contains interfaces for additional sensors. The system in particular applies to buildings and structures for transport and traffic and large-scale industrial facilities, where a subsequent wiring installation is difficult or impossible.
A multi-sensor system for 3D localization was developed and named BodyGuard. It combines body movement sensing and a guard system for the tracking and recording of the status of persons. BodyGuard was designed to monitor and transmit the movement of a person radio-based and to transform that data into a spatial coordinate. This paper describes how the BodyGuard system works, what components the system consists of, how the individual sensor data is converted into 3D motion data, with which algorithms the individual sensors are processed, how individual errors are compensated and how the sensor data are fused into a 3D Model.
This paper presents a sampling strategy for mobile gas sensors. Sampling points are selected using a modified artificial potential field (APF) approach, which balances multiple criteria to direct sensor measurements towards locations of high mean concentration, high concentration variance and areas for which the uncertainty about the gas distribution model is still large. By selecting in each step the most often suggested close-by measurement location, the proposed approach introduces a locality constraint that allows planning suitable paths for mobile gas sensors. Initial results in simulation and in real-world experiments with a gas-sensitive micro-drone demonstrate the suitability of the proposed sampling strategy for gas distribution mapping and its use for gas source localization.
Eine Reihe von Prüfproblemen in der chemischen Industrie, in Kraftwerksanlagen und in Transportsystemen ist aufgrund schwieriger Zugangsmöglichkeiten nur begrenzt technisch bzw. wirtschaftlich effizient durchführbar. Das hier vorgestellte Projekt beinhaltet die Entwicklung eines Verfahrens der zerstörungsfreien Prüfung über weite Entfernungen (bis zu 100 m), das zum Einsatz in automatisierten Messsystemen bzw. zur Integration in Langzeitüberwachungssysteme geeignet ist. Grundlage des Verfahrens ist die gezielte Anregung und Auswertung von Lamb-Wellenmoden, wodurch eine effektive Unterscheidung von Fehler- und Formanzeigen sowie eine Klassifizierung unterschiedlicher Fehlertypen möglich werden.
Der Vorteil der Nutzung geführter Wellen für die zerstörungsfreie Prüfung liegt in ihrer vergleichsweise guten Ausbreitungsfähigkeit über weite Entfernungen. Die sich daraus ergebenden Möglichkeiten der Untersuchung großer bzw. schwer zugänglicher Bereiche einer Struktur bieten innovative Ansätze für die Entwicklung robuster Structural-Health-Monitoring-Systeme (SHM). Erst durch die Verfügbarkeit leistungsfähiger Rechentechnik wird ein breiter Einsatz derartiger Verfahren möglich. Die Technik kann zur Materialcharakterisierung an ebenen bzw. zylindrischen, dünnwandigen Flächen aus Metall oder auch CFK genutzt werden. Adressierte Anwendungsfelder sind z.B. die Untersuchung von Flugzeugtragflächen oder Pipelines. Des Weiteren wird der Einsatz solcher Verfahren zur Überwachung sicherheitsrelevanter Bauteile z.B. aus Laminaten angestrebt, wie sie verstärkt in der Luft- und Raumfahrt Anwendung finden. Im Rahmen des Projekts wurde auf Grundlage vorhandener Technik (Wellenanregung mittels Ultraschall-Gruppenstrahlprüfköpfen) ein umfassendes Verständnis für die Technologie und anwendungsrelevante Parameter (Probenmaterial und -dimensionen, Welleneigenschaften, Anregungs-, Transmissions-, Reflektionscharakteristika) gewonnen und Algorithmen zur Erkennung von Schädigungsbildern (z.B. Riss, Loch, Verdünnung) entwickelt.
Neben der Algorithmusentwicklung zur Detektion und Analyse von Schadstellen, lag ein Projektschwerpunkt in der Entwicklung einer geeigneten Gerätetechnik. Als sensorisches Elemente wurde Ultraschall-Gruppenstrahlertechnik eingesetzt. Besondere Anforderungen werden an die Technik zur Anregung der Wellenmoden unter Verwendung geeigneter Piezoaktoren gestellt. In diesem Bereich existiert bislang keine kommerziell erhältliche Gerätelösung, weshalb eine Neuentwicklug der Anregetechnik realisiert wurde. Speziell für die hohe Anzahl an Aktorkanälen, die benötigt wird, um unterschiedliche Moden und Wellenformen anzuregen, wurde eine äußerst leistungsfähige Anregeeinheit entwickelt.
Dehnungsmessstreifen (DMS) gehören zu den Standardsensoren beim Messen mechanischer Größen.
Sie finden Ihre Anwendung auf unterschiedlichen Gebieten, als sensorische Komponente in
Messaufnehmern (z.B. Wägezelle, Kraftaufnehmer) oder für Dehnungsmessungen im Bereich der
Strukturüberwachung unter anderem an Brücken oder Bauwerken. Sie werden in verschiedenen Größen
geliefert und mit entsprechenden Klebstoffen auf der Objektoberfläche des Messobjekts an der jeweiligen
Messstelle angebracht und an das Messsystem angeschlossen. Dieser Aufbau wird bei den
verschiedenen Anwendungen unterschiedlichen Temperaturen und Umwelteinflüssen ausgesetzt. Dabei
wird das System DMS/Klebstoff in seinen Eigenschaften verändert und das Ergebnis der
Dehnungsmessung beeinflusst. Beispielsweise kann es zu einer Verfälschung der Messergebnisse
kommen, wenn der Klebstoff die Dehnung des Messobjekts nicht vollständig auf den DMS überträgt, oder
es kann eine Nullpunktverschiebung der Dehnungsmessung auftreten.
An der Bundesanstalt für Materialforschung und -prüfung werden Fallversuche von Lager- und
Transportbehältern durchgeführt. Für diese werden Dehnungsmessstreifen auf den Behälter angebracht
um die Dehnung bzw. Verformung zu messen. Bei den Versuchen werden verschiedene Parameter
berücksichtigt: Neben unterschiedlichen Fallhöhen (u.a. 9 m und 1 m) wird auch der Temperatureinfluss
auf den Fallversuch z.B. bei -40 °C oder +100 °C untersucht. Zur Applizierung von DMS auf
Objektoberflächen gibt es für verschiedene Anwendungsbedingungen (DMS-Typ, Objektoberflächenbeschaffenheit,
Einsatztemperatur) von den DMS-Herstellern jeweils empfohlene Klebstoffe.
Insbesondere für Anwendungsfälle mit hochdynamischer Belastung (Fallversuche, Crash-Tests) und
großem Temperaturbereich ist es erforderlich, dass die Dehnungsmessstreifen zuverlässige Werte
ausgeben. Dies ist nur gegeben, wenn der Klebstoff eine gute Verbindung zwischen Messobjekt und
Dehnungsmessstreifen herstellt.
Sensor based person tracking is a challenging
topic. The main objective is positioning in areas without
GPS connection, i.e. indoors. A research project is carried
out at BAM, Federal Institute for Materials Research and
Testing, to develop and to validate a multi-sensor system for
3D localization. It combines body motion sensing and a
guard system for the tracking and recording of the status of
persons. The so named BodyGuard system was designed for
sensor-based monitoring and radio-based transmission of
the movement of a person. Algorithms were developed to
transform the sensor data into a spatial coordinate. This
paper describes how the BodyGuard system operates, which
main components were used in the system, how the
individual sensor data are converted into 3D motion data,
with which algorithms the individual sensors are processed,
how individual errors are compensated and how the sensor
data are merged into a 3D Model. Final objective of the
BodyGuard system is to determine the exact location of a
person in a building, e.g. during fire-fighting operations.
The Split Hopkinson Pressure Bar (SHPB) or
Kolsky Bar is known as a method for analysing
mechanical properties of a material under dynamic
load. Referring to the name it is a splitted
Hopkinson Pressure Bar. The Hopkinson Bar is
related to its inventor Bertram Hopkinson (1914).
He used it to analyze stone samples under dynamic
load. Later his construction was improved by
Davies (1948) [1] and Kolsky (1949) [2], who had
the idea to split the bar and put a sample in
between.
The technique is used to measure a lot of
different mechanical properties of a material e.g.
the dynamic Youngs modulus, deformation
behaviour or to chart the dynamic stress-strain
diagram. Further applications are the measurement
of the elastic wave and the analysis of the
propagation of the wave [2]. In the last years there
was still an interest in measuring dynamic
properties with a SHPB. Nevertheless no
comprehensive validation of the system exists.
Another problem is that the stress and the strain in
the sample are only calculated with simplified
estimations.
The aim of this paper is to give a first
impression of important points validating the
system. On account of different setups of the
SHPB a validation of the used system is necessary.
Hence it is important to look at the theory. Further
in this paper the measurement results will be
shown in a strain over time diagram.
In this study a method for early damage detection is investigated based on the directed excitation and measuring of Lamb waves (guided waves). The objective is to make a statement about the practicability of a Lamb wave generator (LWG) and about the application relevant parameters (specimen materials and dimensions, wave characteristics, excitation, transmission und reflection). Guided waves enable an effective differentiation of structural and defective indications as well as a classification of different defect types. For the investigations, a LWG was developed which combines the advantages of the single excitation of a piezoelectric actuator and the possibility of a group excitation. Algorithms were developed to identify and analyze damage patterns (cracks, wholes, weakening).